1903Collector
NES Member
Did it feel sluggish at all when you fired it?
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AR Bolt Won't Lock Back
- Thread starter Ninsho
- Start date
Care to qualify 'sluggish'? I don't think it felt sluggish, but then again I don't have much experience with other ARs to compare it with.
I think so... I haven't exactly measured the speed of it or anything, but in the past I have been able to fire it pretty much as fast as I can pull the trigger. I haven't been able to tell that anything was out of the ordinary.
1903Collector
NES Member
You would know if it was..You would feel it as you fired. I remember one of the techs at Bushmaster had me remove the BCG, put the bolt in the forward position then put some oil around the base of the carrier key. Then take a straw and put in carrier key hole and blow air into it. The idea being if there is a gas leak you would hear and see the air escaping around the base of the key. Thant's how I found my problem but like I said earlier that seems to be a rare occurance. Maybe it just needs to broken in some more? I remember a while back someone here suggesting that new ARs should be run "wet" when they are new. Anyway good luck on solving your problem...You have probably done this already but you might try breaking it all down and checking everything over carefully.
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![[wink]](/xen/styles/default/xenforo/smilies.vb/002.gif "Wink [wink]")
.Generally this can be caused by the following problems:
1. Bad magazines (weak springs). Try new, high quality magazines.
2. Weak ammo. If your using low quality Wolf, maybe the occasional round is under-powered. Although, be careful with this one. Your gun should still work properly with the reduced power of standard .223/Wolf. High powered XM193 just masks gas leaks and other problems.
3. Gas block/tube leak or gas block misalignment. If the gas block (front sight post if A2 rifle) is misaligned, the hole in the barrel could be blocked. Another possibility is that the gas block doesn't make a good seal with the barrel. Did the gas tube roll pin come out of the gas block?
4. Gas tube wear. After many rounds, or if gas tube was bent, the flange or "mushroom" on the end of the gas tube in the receiver can get worn down to the point where it no longer makes a good seal. Try measuring with some good calipers the outside diameter of the end of the gas tube all around. Compare that to the inside diameter of the bolt carrier key hole. The gas tube should be about 0.176", while the key hole should be 0.1805".
5. Worn or misaligned bolt gas rings. Make sure the three rings around the bolt are aligned such that the gaps in the rings are all 120 degrees apart (equi-spaced). Otherwise, you can get gas leaks.
6. Junk in the buffer tube. This is pretty unlikely, but if your buffer tube has tons of crud in it, maybe it is getting bound up when the bolt travels back. Try cleaning the buffer.
7. Loose carrier key on bolt carrier. This is hard to fix yourself. Need to send it back so they can properly re-torque and stake the two bolts that hold the carrier key to the carrier.
1. Bad magazines (weak springs). Try new, high quality magazines.
2. Weak ammo. If your using low quality Wolf, maybe the occasional round is under-powered. Although, be careful with this one. Your gun should still work properly with the reduced power of standard .223/Wolf. High powered XM193 just masks gas leaks and other problems.
3. Gas block/tube leak or gas block misalignment. If the gas block (front sight post if A2 rifle) is misaligned, the hole in the barrel could be blocked. Another possibility is that the gas block doesn't make a good seal with the barrel. Did the gas tube roll pin come out of the gas block?
4. Gas tube wear. After many rounds, or if gas tube was bent, the flange or "mushroom" on the end of the gas tube in the receiver can get worn down to the point where it no longer makes a good seal. Try measuring with some good calipers the outside diameter of the end of the gas tube all around. Compare that to the inside diameter of the bolt carrier key hole. The gas tube should be about 0.176", while the key hole should be 0.1805".
5. Worn or misaligned bolt gas rings. Make sure the three rings around the bolt are aligned such that the gaps in the rings are all 120 degrees apart (equi-spaced). Otherwise, you can get gas leaks.
6. Junk in the buffer tube. This is pretty unlikely, but if your buffer tube has tons of crud in it, maybe it is getting bound up when the bolt travels back. Try cleaning the buffer.
7. Loose carrier key on bolt carrier. This is hard to fix yourself. Need to send it back so they can properly re-torque and stake the two bolts that hold the carrier key to the carrier.
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This is highly unlikely to be the problem. The gas operating system of the AR is very finicky. If you can inspect the bolt catch and see that it is not broken or cracked (and it locks back fine when you pull the charging handle) its not that.
![[smile]](/xen/styles/default/xenforo/smilies.vb/001.gif "Smile [smile]")
This is a direct quote from my instructor when I took Colt's Armorers M16/AR15 course "The last round fired from a magazine that does not keep the bolt carrier group back is a loose gas key" - Mike Heath (instructor) this can be fixed with red loktite. Other possibilities are a clogged or restricted gas tube, restriction of the buffer, buffer tube, or spring. If it were a faulty mag chances are it would only be that mag. If it was bolt catch problem chances are it would happen with every mag
Mixed luck this morning at the range. Bolt was still not locking back for the first few magazines I tried. For shits and giggles I tried loosening the stock screw, and the bolt started locking back sporadically (prior to this it has been at least 10 magazines or more since it has locked back).
Based on this I am really wondering if its possible that there is some sort of obstruction caused by the screw. I am also wondering what else that screw might change by having the stock tight or loose.
Is anyone who is an expert on such things going to the Pumpkin Shoot? If so would you mind taking a look and see if anything seems messed up?
Based on this I am really wondering if its possible that there is some sort of obstruction caused by the screw. I am also wondering what else that screw might change by having the stock tight or loose.
Is anyone who is an expert on such things going to the Pumpkin Shoot? If so would you mind taking a look and see if anything seems messed up?
First of all, thanks JohnFH and MassMark for the assistance yesterday at the range, got me a lot further with trying to figure out my AR's issues than I could have gotten on my own.
It appears the .223 isn't hot enough to reliably lock the bolt back, and the bolt seems to struggle coming back when pulling on the charging handle. I took the rifle down this morning and tried cleaning out the buffer tube, there was barely anything to clean out. I think I might have figured out the cause of the hangups though: it appears that they happen just as the bolt would be sliding over the hammer. Does this seem like a logical conclusion to make, and how might I remedy it?
Thanks again!
It appears the .223 isn't hot enough to reliably lock the bolt back, and the bolt seems to struggle coming back when pulling on the charging handle. I took the rifle down this morning and tried cleaning out the buffer tube, there was barely anything to clean out. I think I might have figured out the cause of the hangups though: it appears that they happen just as the bolt would be sliding over the hammer. Does this seem like a logical conclusion to make, and how might I remedy it?
Thanks again!
Yeah I did. A guy on AR15 just told me to check the trigger disconnect, which shows a line of wear where the hammer has been meeting it. I guess my hammer is too long and has been wedging between the bolt and the trigger disconnect and I need to take like 0.040" off of it. I'm not 100% sure if this will fix the bolt problem, but it should make the charging handle pull smoother. Too bad I need to wait until next Saturday to have the time to try making the change.
